Challenges of the May 4 Flood Event Response in Southeast Texas
Texas DPS Region 2
Beginning May 4, 2015, much of Texas endured a series of severe weather events that produced unprecedented flooding, including a large portion of the counties that make up Texas Department of Public Safety Region 2. Of the 35 counties in Region 2, 24 experienced varying degrees of flooding that ranged from minor to catastrophic levels. The continual downpour from back-to-back events, compounded by a cascading watershed, created one of the most complex and challenging flood responses in recent history.
Trinity, Neches, Brazos and Sabine River flowing into DPS Region 2.
As heavy rains saturated the soil in North Texas and forced massive run off into the Trinity, Neches, Brazos and Sabine River headwaters, a widespread flooding incident rapidly began to unfold. While North Texas was experiencing its own flood of record, Southeast Texas was also being inundated with heavy and continuous rainfall. Soon, the continued rainfall had nowhere to go and began overflowing from most rivers, tributaries, bayous and streams. Communities above the Lake Livingston, Sam Rayburn and Toledo Bend Reservoir dams began to flood as water was unable to pass through the dams fast enough. Even with flood control measures activated along these river systems, massive volumes of water rushed into and out of the reservoirs onto saturated ground downstream.
Flood damage in Southeast Texas.
Communities downstream began to experience some of the worst flooding since the area was devastated when the remnant of Pacific Hurricane Rosa stalled over Texas in 1994. Areas along the lower Trinity, Neches, Brazos and Sabine rivers quickly began to flood, and the rising water flooded homes and made many roads through the region impassable. Flood waters continued to rise throughout the month of May and into early June, until the rivers crested and began an agonizingly slow decline. (As of late July, there are still roads that remain impassable along the Trinity River in Liberty County and the Neches River in North Orange County.)
Flooding in Houston.
At the same time serious flooding was already occurring in the city of Houston and around large parts of Harris County, a severe thunderstorm struck the very same area May 25, lasting for over eight hours. The result was an incredible 12 to 13 inches of rain that fell over a very short time on top of a relatively small, already-saturated area. Along the Braez and Buffalo Bayou areas, over 4,000 homes were quickly flooded. There was just nowhere for this large amount of rainfall to go. Flash flooding occurred over roads and highways in the affected area, overtaking hundreds of vehicles, stranding motorists and, in some instances, resulting in the loss of life. Southeast Texas sees its fair share of rain, but rarely has the region experienced such a level of flooding caused by a combination of intense localized heavy rainfall coupled with five weeks of almost continuous rain and exacerbated by rising water from upstream river flooding.
Flood damage in Southeast Texas.
Compounding the Situation
On top of everything that was happening, Tropical Storm Bill made landfall on June 15 around the Matagorda Bay area on the mid-Texas Coast. Flooding rains from T. S. Bill covered most of Southeast Texas and tracked northeasterly into the North Texas area, reigniting flood issues. Areas that had already experienced flooding from the May 4 flood incident were once again affected by more torrential rains. Areas along the lower end of the Brazos and Colorado rivers experienced high rainfall totals, halting the fall of those rivers and extending the flooding event. On June 17, the trailing rain bands associated with T. S. Bill impacted the communities in Jasper and Newton counties. A staggering 13 inches of rain fell in a six-hour period in these communities, resulting in flash flooding that inundated homes and roads. Many of these areas might have been spared from such extreme flooding had it not been for the unfortunate timing of T. S. Bill.
The combined effect of flooding beginning on May 4 with the flash flood incident on May 25 in the Houston area and finally T. S. Bill’s landfall on June 15 created a large-scale flood event rarely seen before in Southeast Texas. Many local jurisdictions quickly exhausted on-hand emergency response resources and began requesting state resources for assistance. Traditionally, flooding is the most significant severe weather threat to areas in Southeast Texas that extend to the upper Texas Coast, and most local first responders and emergency managers in the region have had plenty of experience dealing with flooding at some point in their careers. However, the combination of all three incidents within a relatively short time period is something that very few people in this area, including emergency management professionals, have ever encountered before.